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Molecular structure, NBO analysis, ?rst hyper polarizability, and homo-lumo studies of π-extended tetrathiafulvalene (EXTTF) derivatives connected to π-nitro phenyl by density functional method
摘要： In these study we have been obtained the structural properties of (exTTF) derivatives 1-4 by using B3LYP/6-31G(d,p) of Density Functional Theory (DFT) utilizing Becke three exchange functional and Lee Yang Paar correlation functional. The calculation of first hyperpolarizability shows that the molecules are attractive molecules for future applications in non-linear optics. Molecular electrostatic potential (MEP) at a point in the space around a molecule gives an indication of the net electrostatic effect produced at that point by the total charge distribution of the molecule. The calculated HOMO and LUMO energies show that charge transfer occurs within these molecules.
关键词： Density Functional Theory,Quantum Chemical Calculations,Computational Chemistry,Electronic Structure,Tetrathiafulvalenes
更新于2025-09-23 15:23:52
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UV photolysis of tetrachloro-p-benzoquinone (TCBQ) in aqueous solution: Mechanistic insight from quantum chemical calculations
摘要： In this work, a systematical investigation on the transformation of tetrachloro-p-benzoquinone (TCBQ) under UV irradiation (at 253.7 nm) in aqueous solution has been conducted through quantum chemical calculations. The UV irradiation at 253.7 nm could induce the excitation of TCBQ to its first excited singlet state, followed by the intersystem crossing to its first triplet state. In aqueous solution, the first triplet state of TCBQ was thermodynamically and kinetically feasible to react with H2O via 1,4-addition, where the addition of OH- to the α–β conjugated system was the dominant step. Interestingly, with the addition of hydroxyl to TCBQ, the dechlorination of TCBQ occurred with the formation of the monohydroxylated product of TCBQ (OH-TriCBQ). The UV photolysis pathway of OH-TriCBQ was similar to that of TCBQ, and the 1,4-addition of OH- to the ortho-position of the hydroxyl was the most efficient pathway. The dechlorination by 1,4-addition of OH- was also observed for OH-TriCBQ. With much larger forward energy barriers, the nucleophilic addition of carbonyl by OH- (i.e., 1,2-addition) might be less important for the UV photolysis of TCBQ and OH-TriCBQ. The findings in the present study may help to understand the transformation of TCBQ in aqueous solution.
关键词： UV irradiation,Quantum chemical calculations,Dechlorination,Tetrachloro-p-benzoquinone
更新于2025-09-23 15:23:52
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Molecular engineering of highly efficient dopant-free spiro-type hole transporting materials for perovskite solar cells
摘要： Up to now, the most efficient perovskite solar cells (PSCs) typically utilize Spiro-OMeTAD as hole transporting materials (HTMs). The unique “spiro” structure offers appropriate energy levels for hole transfer and high thermal stability with suppressed aggregation. However, the pristine Spiro-OMeTAD requires additional oxidizing dopants to work efficiently due to its low hole mobility. To retain the advantages of spiral structure and overcome its shortcomings, we demonstrate the design of three dopant-free HTMs with spiral structure by molecular engineering, in which three groups with different conjugated lengths, namely benzene, naphthalene and anthracene, are inserted between spiral core and electron donor. These designed molecules, Y-1~Y-3, are initially identified with quantum chemical calculations based on the mother molecule X59 and then are obtained by easy synthetic routes. Our studies show that the intramolecular charge transfer (ICT) states are formed in the designed molecules due to the introduction of conjugated groups, which produces a self-doping effect without the need to add any external dopant. The best-performing PSCs using the dopant-free Y-1 as HTM achieves a champion power conversion efficiency (PCE) of 16.29% under one sun illumination, which is higher than that of devices with X59 as dopant-free HTMs (14.64%). The present work provides an effective strategy for designing, synthesizing of highly efficient and stable dopant-free HTMs.
关键词： Perovskites solar cells,Dopant-free,Hole-transporting materials,Quantum chemical calculations,Spiral structure
更新于2025-09-23 15:19:57
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Formation of a supramolecular charge-transfer complex. Ultrafast excited state dynamics and quantum-chemical calculations
摘要： The formation of a supramolecular complex of bis(18-crown-6)stilbene (1) and 4,4’-bipyridine with two ammoniopropyl N-substituents (3) and the substitution reaction between 1·3 and alkali and alkaline-earth metal perchlorates have been studied using absorption, steady-state fluorescence, and femtosecond transient absorption spectroscopy. The formation of 1·(Mn+)2 complexes in acetonitrile was demonstrated. The weak long-wavelength charge-transfer absorption band of 1·3 completely vanishes upon complexation with metal cations because of disruption of the pseudocyclic structure. The spectroscopic and luminescence parameters, stability and substitution constants were calculated. The relaxation scheme of the 1·3 singlet state excited by a 25 fs laser pulse was proposed. It includes very fast vibrational relaxation and direct (τCT-d = 0.32 ps) and back (τCT-b = 0.51 ps) electron transfer resulting in complete fluorescence quenching. The quantum-chemistry calculations revealed the species taking part in the ET process and elucidated the mechanism of relaxation of the excited complex.
关键词： supramolecular complex,quantum-chemical calculations,femtosecond spectroscopy,charge-transfer,electron transfer
更新于2025-09-19 17:15:36
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Infrared-Spectroscopic Study of (4-Methylpent-3-en-1-ynyl)methylthiocarbene, Its Photochemical Transformations, and Reactions in an Argon Matrix
摘要： The first representative of singlet carbenes bearing both ethynyl and methylthio groups at the carbene center, (4-methylpent-3-en-1-ynyl)methylthiocarbene, has been generated in a low-temperature Ar matrix upon UV photolysis of 3,3-dimethyl-5-methylthioethynyl-3H-pyrazole and detected by FTIR spectroscopy. The generation of the carbene proceeds via intermediate (3-diazo-5-methylhex-4-en-1-ynyl)methylsulfane. The comparison of FTIR spectroscopy data with the results of quantum chemical calculations (B3LYP/aug-cc-pVTZ) and NRT analysis shows that (4-methylpent-3-en-1-ynyl)methylthiocarbene has a singlet ground state with the localization of the unpaired spins on the carbon atom in the α-position to methylthio moiety. Two major pathways of further phototransformation of the studied carbene have been found. One of them produces photochemically stable thioketone (SCMe?CC?CHCMe2) as a result of methyl group migration from sulfur to the neighboring carbon atom, and the other one leads to the labile thioketene (SCC(Me)?CHCH?CMeCH2). Ability of (4-methylpent-3-en-1-ynyl)methylthiocarbene to insert into the H?Cl bond was established, which additionally confirms the singlet nature of this intermediate.
关键词： H?Cl bond insertion,quantum chemical calculations,FTIR spectroscopy,thioketene,singlet carbenes,methylthio groups,ethynyl,phototransformation,thioketone
更新于2025-09-19 17:13:59
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IR‐Laser Ablation of Potassium Cyanide: A Surprisingly Simple Route to Polynitrogen and Polycarbon Species
摘要： Pulsed laser irradiation of solid potassium cyanide (KCN) produces, besides free nitrogen and carbon atoms, the molecular species KN and KC which are potential candidates for interstellar species of potassium. Additionally, N3, N3?, and KC3 are produced and isolated in solid noble gases as well as in solid N2. Molecular potassium nitrene (KN) reacts with dinitrogen in neon and argon matrices after photochemical excitation (λ = 470 nm) forming molecular end-on (C∞v) and side-on (C2v) potassium azide isomers. The side-on isomer (C2v) is thermodynamically favored at the CCSD(T)/ma-def2-TZVP level of theory. It can be obtained from the end-on isomer by UV-irradiation (λ = 273 nm).
关键词： Laser Ablation,Quantum-Chemical Calculations,Polycarbon Compounds,Polynitrogen Compounds,Matrix-Isolation Spectroscopy
更新于2025-09-16 10:30:52
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Triplet–triplet upconversion enhanced by spin–orbit coupling in organic light-emitting diodes
摘要： Triplet–triplet upconversion, in which two triplet excitons are converted to one singlet exciton, is a well-known approach to exceed the limit of electroluminescence quantum efficiency in conventional fluorescence-based organic light-emitting diodes. Considering the spin multiplicity of triplet pairs, upconversion efficiency is usually limited to 20%. Although this limit can be exceeded when the energy of a triplet pair is lower than that of a second triplet excited state, such as for rubrene, it is generally difficult to engineer the energy levels of higher triplet excited states. Here, we investigate the upconversion efficiency of a series of new anthracene derivatives with different substituents. Some of these derivatives show upconversion efficiencies close to 50% even though the calculated energy levels of the second triplet excited states are lower than twice the lowest triplet energy. A possible upconversion mechanism is proposed based on the molecular structures and quantum chemical calculations.
关键词： Triplet–triplet upconversion,spin–orbit coupling,anthracene derivatives,quantum chemical calculations,organic light-emitting diodes
更新于2025-09-11 14:15:04
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Electronic Spectra of Graphene in Far- and Deep Ultraviolet Region. Attenuated Total Reflection Spectroscopy and Quantum Chemical Calculation Study
摘要： We measured the electronic spectra of graphene nanostructures (flakes and platelets) extending into far-ultraviolet (FUV) region by attenuated total reflection far- and deep-ultraviolet (ATR-FUV-DUV) spectroscopy in the region of 2.76-8.55 eV (450-145 nm). The major absorption of graphene appears in the DUV region (4.7 eV), as already reported, however, we observed a new peak in the FUV region; visible clearly in the case of the flakes at 7.5-7.7 eV (165-161 nm) and less pronounced in the spectrum of the platelets at 6.6-6.7 eV (188-185 nm). Graphene flakes (thickness 1-2 nm; sub-micrometers of side dimension) and nanoplatelets (thickness 6-8 nm; several micrometres of side dimension) give notably different ATR absorbance spectra in the spectral region studied. This discrepancy is reduced upon applying mechanical pressure on the samples. These observations can evidence that the morphology as well as electronic structure of graphene can be manifested in the FUV-DUV region. Quantum chemical calculations were applied to several molecular models incorporating the expected principal structural features of graphene nanostructures. Based on the results of time-dependent density functional theory (TD-DFT) and Zerner's intermediate neglect of differential overlap (ZINDO) calculations, it was possible to consistently reproduce the experimental spectral variations in terms of both band positions and intensities. The spectral differences result from the differences in the die area, ordering and the number of layers; structural factors which separate nanoflakes and nanoplatelets. These results provide insights into the probable origins of the spectral variability of graphene nanostructures as well as the molecular orbitals involved in a FUV π-π* transition of graphene nanostructures.
关键词： far-ultraviolet,quantum chemical calculations,ATR spectroscopy,graphene,deep-ultraviolet
更新于2025-09-10 09:29:36